Process of making chromates.



N0. 784,640. Patented March 14, 1905.

UNITED STATES PATENT OFFICE.

ROBERT SUOHY, OF GRIESHEINLON-THE-MAIN, GERMANY, ASSIGNOR TO GHEMISCHE FABRIK GRIESHEIM ELECTRON-OF FRANKFORl ON-THE- MAIN, GERMANY.

PROCESS OF MAKING OHROMATES.

SPECIFICATION forming part of Letters Patent No. 784,640, dated March 14, 1905.

Application filed July 16. 1903- Serial No. 165,839.

T whom it y wern: tic potash that has not been transformed into Be it known that 1, ROBERT SUOHY, a subchromate as caustic-potash lye or carbonate ject of the Emperor of Austria-Hungary, reof potash. This fact, together with the low siding and having my post-oflice address at temperature and the consequent large saving 5 1 Tahnstrasse, Griesheim-on-the-Main, Gerof fuel, renders it possible to carry out the many, have invented certain new and useful process cheaply in spite of the high cost of Improvements in Rendering Soluble Chromecaustic potash. 55 Ironstone, of which the following is a spec1fi- The process is carried out as follows: cat1on. Finely-pulverized chrome-ironstone and caus- 1 The process forming the object of the prestic potash in the form of a lye of 50 Baum are cut invention has for its purpose to make heated and energeticallystirred in a suitable chromates from chrome-ironstone (and more furnace in the proportion of one hundred to 60 especially potassium chromate) more cheaply two hundred and fifty, by weight. The oxidaand more readily than by the processes hithtionbegins,asalreadystated,at3O0 centigrade erto known. and goes on smoothly and completely at 500.

The extraversion of the ore of chromium, The melt obtained is yellow green and is lixwas hitherto effected by mixing the finely puliviated and freed of impurities (aluminates 5 verized material with a large amount of carand silicates) by the addition of lime or by bonate of soda and lime or of carbonate of passing carbon dioxid through it. After tilpotash and lime and subjecting the mixtration the lye, which contains only potasture to a high temperature. Saltpeter was sium chromate and caustic potash or carbonalso frequently added as oxidizing agent. ate of potash, is evaporated, the potassium 7 (See Dammor III, 539.) It has, however, chromate being almost entirely precipitated, been found that such high temperatures are while the excess of KOH remains as potash 5 not at all necessary, if in lieu of the aforelyeor carbonate of potash and may be utilmentioned chemicals caustic potash is allowed ized for a further operation or other purto act on the chrome-ironstone and a liberal poses. The salt can be readily extracted with 75 supply of air is provided. For analytical pura little water. poses a mixture of caustic soda and caustic pot- It will be seen that the process runs smoothly 3 ash has often been proposed for the extraverand yields an almost chemically pure product sionof chromium ore. This, however, requires and but few waste products, being in this rethe use of a blast. \Vhile, as already stated, spect far superior to the methods hitherto the processes hitherto known required atemknown, in which the lixiviation of the highlyperature of over 1,000 centigrade, the extraheated melts presented considerable difficulversion by means of caustic potash'takes ties.

place already at about 300 centigrade, as Having now particularlydescribed and astrials have already shown. The more enercertained the nature of this invention and in 8 5 getic oxidizing action of the caustic potash as what manner the same is to be performed, 1 compared with that of caustic soda, carbonate declare that what I claim is 4 of soda, or of potash and the like is in any case 1. The process of makingchromates, which attributable to the fact that molten KOH abconsists in subjectinga mixture of pulverized sorbs oxygen from the air and forms a superchrome ore and caustic potash to a ten'ipera- 9 oxid which is amuch more effectual oxidizing ture not exceeding 500 centigrade in the agent than the aforementioned substances. presence of air, and agitating the mixture Although caustic potash is more costly than during the period of heating.

the aforesaid substances, this is for the pres- 2. The process of making chromates which cut process of no importance, as it is possible, consists in subjecting a mixture of pulverized 95 as shown hereinafter, to recover all the causchrome ore and a caustic-potash lye of Baum, in substantially the proportions of the period of heating, lixiviating the melt and one hundred to two hundred and fifty by freeing it from impurities, and separating the weight, to a temperature not exceeding 500 chromate from the lye by evaporation. centigrade in the presence of air, and agitatlntestimony whereoflhave signed my name 5 ing the mixture during the period of heating. to this specification in the presence of tWo sub- 5 3. The process of making chromates, which scribing Witnesses.

consists in subjecting a mixture of pulverized ROBER' SUCHY. chrome ore and caustic potash to a tempera- W itnesses: ture not exceeding 500 centigrade in the FRANZ HAssLAcHER,

1O presence of air, agitating the mixture during MICHAEL VOLKE. 

